I had a discussion this morning with customer about a part where they had a plane as Datum A and a pattern of clearance holes as Datum B and considered that as a complete reference frame.

After the call, I did a little research and apparently this is a thing that people do.  There's a bit of content in the 2009 standard about it and I saw some references to relevant content in the 2018 standard, but I don't have a copy of that yet.  

Does CMM manager have the capability to *directly* deal with this type of situation, i.e. locate and align to a pattern?  In the case of this part, it's a round pattern, and he's got his origin as one of the holes in the pattern, NOT the center of the pattern.  So it's probably going to require a bit of improvisation to program it anyway, but I thought I'd put this out there and see what folks think.

As an aside, I can’t really say that I’m a fan of this method, because I think that it conflicts with the diamond pin concept (i.e. for a simple plate with two holes, using a round pin for Datum B and a diamond pin for Datum C to avoid over constraining while orienting with second round pin).  

Thoughts or experiences to share?